Oxygen Atoms Of CO Research Articles

Efficient Selective Capture of Carbon Dioxide from Nitrogen and Methane Using a Metal-Organic Framework-Based Nanotrap

Selective carbon capture from exhaust gas and biogas, which mainly involves the separation of CO2/N2 and CO2/CH4 mixtures, is of paramount importance for environmental and industrial requirements. Herein, we propose an interesting metal-organic framework-based nanotrap, namely ZnAtzCO3 (Atz− = 3-amino-1,2,4-triazolate, CO32− = carbonate), with a favorable ultramicroporous structure and electrostatic interactions that facilitate efficient capture of CO2. The structural composition and stability were verified by FTIR, TGA, and PXRD techniques. Particularly, ZnAtzCO3 demonstrated high CO2 capacity in a wide range of pressures, with values of 44.8 cm3/g at the typical CO2 fraction of the flue gas (15 kPa) and 56.0 cm3/g at the CO2 fraction of the biogas (50 kPa). Moreover, ultrahigh selectivities over CO2/N2 (15:85, v:v) and CO2/CH4 (50:50, v:v) of 3538 and 151 were achieved, respectively. Molecular simulations suggest that the carbon atom of CO2 can form strong electrostatic Cδ+···δ−O-C interactions with four oxygen atoms in the carbonate ligands, while the oxygen atom of CO2 can interact with the hydrogen atoms in the triazolate ligands through Oδ−···δ+H-C interactions, which makes ZnAtzCO3 an optimal nanotrap for CO2 fixation. Furthermore, breakthrough experiments confirmed excellent real-world separation toward CO2/N2 and CO2/CH4 mixtures on ZnAtzCO3, demonstrating its great potential for selective CO2 capture.

CO2 Capture by Diamines in Dry and Humid Conditions: A Theoretical Approach.

This work is a mechanistic study of the CO2 reaction with diamines under both dry and wet conditions. All protic α,ω-diamines R1H1N1-(CH2)n-N2H2R2, with n = 1-5 and R1 and R2 = H and/or CH3, were investigated. Depending on the nature of the diamine, the reaction was found to follow one of two concerted asynchronous reaction mechanisms with a zwitterion hidden intermediate. Both mechanisms involved two processes. The first process consisted of a nucleophilic attack of the nitrogen N1 of the first amine group on the carbon of CO2, accompanied by the transfer of a hydrogen atom H1 from N1 to the nitrogen N2 of the second amine group, leading to the formation of a carbamate zwitterion. The subsequent process corresponds to the transfer of a hydrogen atom H2 from the second amine group N2 to an oxygen atom of CO2, thus ending the reaction by the formation of carbamic acid. The structure of the zwitterion hidden intermediate was determined using the reactive internal reaction coordinates (RIRC), a reaction pathway visualization tool, consisting of a 3D representation of the potential energy versus the internuclear distances N2-H1 and N2-H2, which correspond to the bond being formed and the bond being broken, respectively. The life span of the transitory species, i.e., the zwitterion, was found to depend on the nature of the second amine group. For primary amines, the life span of the zwitterion was "short", whereas for secondary amines, it was "long". The corresponding mechanisms were termed the "early" and "late" asynchronous mechanism, respectively. Regardless of the mechanism, the activation barriers were found to decrease with the length of the carbon chain linking the two amine groups, with an asymptotic behavior from n = 4. Involvement of a water molecule generates a significant catalytic effect for diamines with short carbon chains (n < 4), whereas for longer chain diamines, water has a slightly adverse effect.

Disilicon Dicarbonyl Complex: Synthesis and Protonation of CO with O-H Bond.

Reaction of solid NHB-stabilized disilyne (NHB)Si≡Si(NHB) (1, NHB = [ArN(CMe)2NAr]B, Ar = 2,6-iPr2C6H3) with 1 atm of carbon monoxide yielded the first 1,2-disilicon dicarbonyl complex (NHB)(OC)SiSi(CO)(NHB) (2). Hydrolysis and methanolysis of 2 led to the C-C coupling and protonation of two CO oxygen atoms giving disilacyclobutene derivatives 3 and 4. In contrast, reaction of 2 with iodomethane resulted in the oxidative addition to the silicon atoms with the formation of 1,2-diiodo-disilane 5 with the liberation of CO molecules. Single-crystal X-ray diffraction analysis of 2 disclosed the coordination of CO to the two silicon atoms with a unique 1,2-dicarbonyl-disilane skeleton, in which the pronounced backbonding from the lone pairs of silicon p orbitals to CO π* orbitals was elucidated by DFT calculations.

Active and selective reverse water-gas shift reaction over Pt/Na-Zeolite catalysts

The introduction of the frustrated Lewis pair (FLP) concept in heterogeneous catalysis, particularly zeolites, is effective in activating stable molecules, such as CO2. However, regulating the FLP density structure to control the activity and selectivity remains challenging. This study examined the effects of the FLP density and zeolite structure on the reverse water-gas shift reaction using Pt/zeolite catalysts. The reaction results obtained using catalysts with various zeolites showed that the presence of FLP in the zeolite promoted CO2 conversion and CO selectivity, but a high FLP density was not necessarily beneficial. A high density of FLP could delay the intracrystalline diffusion of intermediates and could lower the CO selectivity. Operando infrared spectroscopy and density functional theory calculations suggested that FLP could effectively stabilize the intermediate responsible for CO production through selective hydrogenation of the oxygen atom of CO2 at the initial stage of the reaction.

Understanding the role of Ga on the activation mechanism of CO2 over modified Cu surface by DFT calculation

Ga-containing catalysts show excellent performance in CO2 catalytic utilization. In this research, activation mechanisms of CO2 on Cu Surface modified by Ga with different forms (Cu, Cu8Ga1, Cu6Ga3, and Ga2O3@Cu) were systematically studied by DFT calculations. Combining the thermodynamics with chemical kinetics, the roles of interfacial effect for CO2 activation were revealed. The reaction energy barrier was significantly reduced at the interface between metal surface and Ga2O3. CO2 preferentially activates through CO2→CO2*→HCOO* at the interface. For Ga2O3 supported Cu catalyst, CO2 was transformed into chemisorbed CO2*, while for Cu, Cu8Ga1 and Cu6Ga3 catalysts, CO2 was behaving as physical adsorption. Millikan atomic charge and CO2 charge density difference for different catalyst surfaces were obtained, and it was found that the two oxygen atoms of CO2 gained the same charges for alloy surfaces while at the interface obtained different charges. Two oxygen atoms gained different charges showing the charge imbalance of the CO2 molecule, which was more favorable to the activation of C = O. The interfacial effect formed between the oxide of Ga and the catalyst surface promotes the activation of CO2 molecule.

Efficient extraction of U(VI) from uranium enrichment process wastewater by amine-aminophosphonate-modified polyacrylonitrile fibers

The enrichment and recovery of U(VI) from low-level radioactive wastewater in the process of uranium enrichment is important for the sustainable development of nuclear energy and environmental protection. Herein, a novel amine-aminophosphonate bifunctionalized polyacrylonitrile fiber (AAP-PAN), was prepared for the extraction of U(VI) from simulated and real uranium-containing process wastewater. The AAP-PAN fiber demonstrated a maximum adsorption capacity of 313.6 mg g−1 at pH = 6.0 and 318 K in the batch experiments. During the dynamic column experiment, over 99.99% removal of U(VI) could be achieved by the fiber using multi-ion simulated solution and real wastewater with an excellent saturation adsorption capacity of 132.0 mg g−1 and 72.5 mg g−1, respectively. It also exhibited an outstanding reusability for at least 5 cycles of adsorption process. The mechanism for U(VI) removal was studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis in the assist of simulation calculation. It suggested that the amine and aminophosphonate groups can easily bind uranyl ions due to U(VI) is more likely to combine with oxygen atoms of CO and PO, respectively.

Adsorption and diffusion behavior of CO2/H2 mixture in calcite slit pores: A molecular simulation study

The adsorption and diffusion of gases in porous media are fundamental phenomena that find widespread application in the energy and chemical industries. In this study, we used Grand Canonical Monte Carlo and molecular dynamics simulation methods to evaluate the adsorption and diffusion properties of CO2 and H2 in the calcite silt-like pores. We report the influence of pressure, pore size, and temperature on adsorption isotherms (i.e., total, absolute, and excess) and diffusion coefficients (i.e., self-diffusion, Fick transport diffusion, and Maxwell-Stefan diffusion). The results reveal a greater CO2 adsorption capacity compared to H2 and the easy absorption of the oxygen atoms of CO2 onto the surface of calcite. The adsorption capacities of CO2 and H2 increased together with the pressure, and the pore size had little effect on the absolute adsorption capacity and density distribution of the pure compounds. The interaction energy between calcite and CO2/H2 showed that the calcite had greater affinity for CO2 than for H2. The CO2 diffusion coefficients were smaller than those of H2. The diffusion coefficients of CO2 and the mutual diffusion coefficients of the gas mixture increased with increasing pressure before stabilizing. In contrast, the diffusion coefficients of H2 decreased with an increase in pressure.

Distinct Solvation Structures of CO2 and SO2 in Reline and Ethaline Deep Eutectic Solvents Revealed by AIMD Simulations.

Deep eutectic solvents (DESs) are emerging as an alternative media for the sequestration of greenhouse gases such as CO2 and SO2. Herein, we performed ab initio molecular dynamics (AIMD) simulations to elucidate the solvation structure around CO2 and SO2 in choline chloride-based DESs, namely, reline and ethaline. We show that in all four systems the structures of the nearest neighbor shells around these molecules are distinct. We observe that because of the electrophilic character, the carbon atom of CO2 and the sulfur atom of SO2 are preferentially solvated by the chloride anions. The strength of the correlation between the chloride anions and the sulfur atom is much stronger because of charge transfer, which is more profound in ethaline DES. In both DESs, the choline cations are found to be closer to the oxygen atoms of CO2 and SO2. We observe that upon changing the solute from CO2 to SO2, the nearest neighbor solvation structure changes drastically; while the chloride anions prefer to stay in a circular shell around the carbon atom of CO2, they are found to be much more localized near the sulfur atom of SO2. The solvation shells formed by the urea molecules in reline and EG molecules in ethaline also overlap with that of the chloride anion around CO2. In ethaline, the hydroxyl group of the choline cation is found to be closer to the solute molecules as compared to its ammonium headgroup.

Catalytic role of sodium carbonate in reduction of ferromanganese spinel

This present study investigated the catalytic effect of Na2CO3 on the reduction of ferromanganese spinel (MnFe2O4) using biochar as reducing agent. The reduction of the MnFe2O4-biochar composite briquettes at 1050 °C for 30 min showed that the iron metallization degree of the reduced briquettes increased from 61.1% to 84.2%, with significant decrease of initial reduction temperature due to the addition of 5 wt% Na2CO3. There also existed higher CO and CO2 concentrations in the off-gas in the presence of Na2CO3. According to the first-principles calculations, these differences were attributed to the reaction between Na2CO3 and carbon which produced oxygen vacancies on the Na2CO3 surface. These vacancies were then filled by the oxygen atoms of CO2, forming CO which was desorbed from the surface of Na2CO3 before it participated in the reduction. By creating oxygen vacancies through its reaction with carbon, Na2CO3 played a catalytic role in the reduction process.

Sequestration of CO2 by Phosphatrane Molecules.

The stationary points for the reaction between the CO2 and nine different phosphatranes molecules have been characterized by means of MP2 computational methods. Two minima structures have been located: a pnicogen bonded complex where one of the oxygen atoms of CO2 acts as electron donor and an adduct that presents a covalent P-C linkage. The corresponding transition state structure linking the two minima has also been characterized. In gas phase, the pnicogen bonded complex is more stable than the corresponding adduct except in one case. In contrast, the inclusion of the solvent effect (toluene and THF), reverts the stability, being in all cases the different adducts more stable than the pnicogen bonded complexes. The electronic properties of the systems have been analysed with the Quantum Theory of Atoms in Molecules (QTAIM) and Electron Density Shift (EDS) methods.

Effect of Vapor Pressure Deficit on Gas Exchange in Wild-Type and Abscisic Acid-Insensitive Plants.

Stomata control the gas exchange of terrestrial plant leaves, and are therefore essential to plant growth and survival. We investigated gas exchange responses to vapor pressure deficit (VPD) in two gray poplar (Populus × canescens) lines: wild type and abscisic acid-insensitive (abi1) with functionally impaired stomata. Transpiration rate in abi1 increased linearly with VPD, up to about 2 kPa. Above this, sharply declining transpiration was followed by leaf death. In contrast, wild type showed a steady or slightly declining transpiration rate up to VPD of nearly 7 kPa, and fully recovered photosynthetic function afterward. There were marked differences in discrimination against 13CO2 (Δ13C) and C18OO (Δ18O) between abi1 and wild-type plants. The Δ13C indicated that intercellular CO2 concentrations decreased with VPD in wild-type plants, but not in abi1 plants. The Δ18O reflected progressive stomatal closure in wild type in response to increasing VPD; however, in abi1, stomata remained open and oxygen atoms of CO2 continued to exchange with 18O enriched leaf water. Coupled measurements of Δ18O and gas exchange were used to estimate intercellular vapor pressure, e i In wild-type leaves, there was no evidence of unsaturation of e i, even at VPD above 6 kPa. In abi1 leaves, e i approached 0.6 times saturation vapor pressure before the precipitous decline in transpiration rate. For wild type, a sensitive stomatal response to increasing VPD was pivotal in preventing unsaturation of e i In abi1, after taking unsaturation into account, stomatal conductance increased with increasing VPD, consistent with a disabled active response of guard cell osmotic pressure.

Complexes of Zn(II)-Triazoles with CO2 and H2O: Structures, Energetics, and Applications.

Using a first-principle methodology, we investigate the stable structures of the nonreactive and reactive clusters formed between Zn2+-triazoles ([Zn2+-Tz]) clusters and CO2 and/or H2O. In sum, we characterized two modes of bonding of [Zn2+-Tz] with CO2/H2O: the interaction is established through (i) a covalent bond between Zn2+ of [Zn2+-Tz] and oxygen atoms of CO2 or H2O and (ii) hydrogen bonds through N-H or C-H of [Zn2+-Tz] and oxygen atoms of H2O or CO2, N-H···O. We also identified intramolecular proton transfer processes induced by complexation. Indeed, water drastically changes the shape of the energy profiles of the tautomeric phenomena through strong lowering of the potential barriers to tautomerism. The comparison to [Zn2+-Im] subunits formed with Zn2+ and imidazole shows that the efficiency of Tz-based compounds for CO2 capture and uptake is due to the incorporation of more accessible nitrogen donor sites in Tzs compared to imidazoles. Since [Zn2+-Tz] clusters are subunits of an organometallic nanoporous materials and Zn-proteins, our data are useful for deriving force fields for macromolecular simulations of these materials. Our work also suggests the consideration of traces of water to better model the CO2 sequestration and reactivity on macromolecular entities such as pores or active sites.

Enhanced Activity in Methane Dry Reforming by Carbon Dioxide Induced Metal‐Oxide Interface Restructuring of Nickel/Zirconia

AbstractThe activity of the Ni/ZrO2 catalyst for the dry reforming of methane was significantly enhanced by activation and regeneration in the presence of CO2. Exposure to CO2 maximized and dynamically restructured the Ni–ZrO2 interface, which was critical to obtain a stable catalyst. The ZrO2−x species at this interface was found to act catalytically by accepting and transferring one oxygen atom of CO2 to the Ni surface, which resulted in the release of CO in the decomposition of transiently formed carbonates. This was found to open a fast additional reaction pathway to convert CO2 that eclipsed direct CO2 dissociation on Ni. The kinetically controlled availability of atomic oxygen by this pathway reduced the carbon concentration on the surface, which led to less refractory carbon deposition and more facile regeneration.

Identification of Primary CO in Coal Seam Based on Oxygen Isotope Method

ABSTRACTAnalysis on the source of CO is very important for prevention of coal spontaneous combustion. In this article, a method of identifying primary CO in coal seams based on an oxygen isotope method is proposed through research. Tests on the oxygen isotopes (δ18O) of CO were generated in coal oxidization reaction and coal pyrolysis reaction. It is found that δ18O of CO will reduce with rising temperature in both reactions, with δ18O of CO being 15–20‰ in air atmosphere and that being 25–28‰ in argon atmosphere in the temperature range of 130–220°C, confirming that the sources of oxygen atoms of CO vary with different atmospheric conditions. Through collecting and testing a number of gas samples from the coal seam and roof in the coal mine, their δ18O of CO is found to be 35.2–37.3‰. The result would improve the prevention of coal spontaneous combustion.

Reactions of Copper and Silver Cations with Carbon Dioxide: An Infrared Photodissociation Spectroscopic and Theoretical Study.

The reaction of copper and silver cations with carbon dioxide was studied by mass-selected infrared photodissociation spectroscopy. Quantum chemical calculations were performed on these products, which aided the experimental assignments of the infrared spectra and helped to elucidate the geometrical and electronic structures. The Cu+ and Ag+ cations bind to an oxygen atom of CO2 in an end-on configuration via a charge-quadrupole electrostatic interaction in the [M(CO2)n]+ complexes. The formation of oxide-carbonyl and carbonyl-carbonate structures is not favored for the interaction of CO2 with Cu+ and Ag+. For n = 3 and 4, the n + 0 structure is preferred. [Note on the nomenclature: Using i + j, i denotes the number of CO2 molecules in the first coordination shell, and j denotes the number of CO2 molecules in the second coordination shell.] The two nearly energy-identical n + 0 and (n - 1) + 1 structures coexist in n = 5 and 6. While the six-coordinated structure is favored for [Cu(CO2)n=7,8]+, the n + 0 configuration is dominated in [Ag(CO2)n=7,8]+. The reaction of CO2 with the cationic metal atoms has been compared to that with the neutral and anionic metal atoms, which would have important implications for understanding the interaction of CO2 with reduction catalysts and rationally designing catalysts for CO2 reduction based on cost-effective transition metals.

Hydrolytic cleavage of both CS2 carbon-sulfur bonds by multinuclear Pd(II) complexes at room temperature.

Developing homogeneous catalysts that convert CS2 and COS pollutants into environmentally benign products is important for both fundamental catalytic research and applied environmental science. Here we report a series of air-stable dimeric Pd complexes that mediate the facile hydrolytic cleavage of both CS2 carbon-sulfur bonds at 25 °C to produce CO2 and trimeric Pd complexes. Oxidation of the trimeric complexes with HNO3 regenerates the dimeric starting complexes with the release of SO2 and NO2. Isotopic labelling confirms that the carbon and oxygen atoms of CO2 originate from CS2 and H2O, respectively, and reaction intermediates were observed by gas-phase and electrospray ionization mass spectrometry, as well as by Fourier transform infrared spectroscopy. We also propose a plausible mechanistic scenario based on the experimentally observed intermediates. The mechanism involves intramolecular attack by a nucleophilic Pd-OH moiety on the carbon atom of coordinated µ-OCS2, which on deprotonation cleaves one C-S bond and simultaneously forms a C-O bond. Coupled C-S cleavage and CO2 release to yield [(bpy)3Pd3(µ3-S)2](NO3)2 (bpy, 2,2'-bipyridine) provides the thermodynamic driving force for the reaction.

Carbonyl ligands in modified “picket fence” iron porphyrin complexes: Order and disorder

A new modified “picket fence” porphyrin is synthesized and its six-coordinate iron(II) carbonyl derivatives [Fe(MmacTpivPP)(CO)(Py)] and [Fe(MmacTpivPP)(CO)(1-MeIm)] are characterized by single-crystal X-ray, UV-vis and IR spectroscopies. X-ray structural determinations revealed that both [Fe(MmacTpivPP)(CO)(Py)] and [Fe(MmacTpivPP)(CO)(1-MeIm)] are crystallized in the C2/c space group with 2-fold axes passing through the Fe atoms. The FeCO angle of [Fe(MmacTpivPP)(CO)(Py)] is as small as 172.1°, contrasted to 180° of the same angle in [Fe(MmacTpivPP)(CO)(1-MeIm)]. Short intramolecular interactions are found between the terminal oxygen atom of CO and the carbon atoms of the pickets in [Fe(MmacTpivPP)(CO)(Py)]. The characteristic CO stretching frequencies (νCO) of the two complexes are same at 1965 cm−1.

Theoretical investigation for adsorption of CO2 and CO on MIL-101 compounds with unsaturated metal sites

In present study, the adsorption of CO2 and CO on the metal–organic framework chromium (III) terephthalate (MIL-101) were investigated using generalized gradient approximation with DFT-D correction. Non-covalent interaction analyses (NCI) were also performed to further investigate the interaction between MIL-101 and gas molecules. The theoretical results indicated that the preferential adsorption mode of CO2 on MIL-101 is different with that of CO. The preferential adsorption mode of CO2 on MIL-101 involves one oxygen atom of CO2 (OCO2) coordinating with exposed Cr atoms through dominated Lewis acid–base interaction. The calculation results indicate that the transference from CCO to the exposed Cr atom causes the CO adsorption ability of MIL-101 to be much stronger than its corresponding CO2 adsorption ability. The theoretical investigation reveals the nature and strength of CO2 and CO adsorptions on MIL-101 and facilitates the development of new MOFs with high CO2 or CO adsorption capacity and selectivity.

Physicochemical impact studies of gamma rays on “aspirin” analgesics drug and its metal complexes in solid form: Synthesis, spectroscopic and biological assessment of Ca(II), Mg(II), Sr(II) and Ba(II) aspirinate complexes

Metal aspirinate complexes, M2(Asp)4, where M is Mg(II), Ca(II), Sr(II) or Ba(II) are formed by refluxed of aspirin (Asp) with divalent non-transition metal ions of group (II) and characterized by elemental analysis and spectroscopic measurements (infrared, electronic, 1H NMR, Raman, X-ray powder diffraction and scanning electron microscopy). Elemental analysis of the chelates suggests the stoichiometry is 1:2 (metal:ligand). Infrared spectra of the complexes agree with the coordination to the central metal atom through three donation sites of two oxygen atoms of bridge bidentate carboxylate group and oxygen atom of CO of acetyl group. Infrared spectra coupled with the results of elemental analyzes suggested a distorted octahedral structure for the M(II) aspirinate complexes. Gamma irradiation was tested as a method for stabilization of aspirin as well as their complexes. The effect of gamma irradiation, with dose of 80Gy, on the properties of aspirinate complexes was studied. The aspirinate chelates have been screened for their in vitro antibacterial activity against four bacteria, gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two strains of fungus (Aspergillus flavus and Candida albicans). The metal chelates were shown to possess more antibacterial activity than the free aspirin chelate.

Understanding the Adsorption Mechanism of C2H2, CO2, and CH4 in Isostructural Metal–Organic Frameworks with Coordinatively Unsaturated Metal Sites

An computational study using density functional theory and grand-canonical Monte Carlo simulation that explore the adsorption mechanism of C2H2, CO2, and CH4 to metal–organic frameworks (MOFs) with coordinatively unsaturated metal sites (M-MOF-74, M = Mg and Zn) has been carried out. The theoretical studies reveal that open metal sites have important roles in adsorption. The high CO2 adsorption ability of M-MOF-74 is due to the strong Lewis acid and base interactions between metal ions and oxygen atom of CO2, as well as carbon atom of CO2 with oxygen atoms in organic linkers. Meanwhile, the high C2H2 adsorption for M-MOF-74 is contributed by the strong complexation between the metal ions and the π orbital of C2H2. The different adsorption mechanisms of CO2, C2H2, and CH4 in M-MOF-74 can qualitatively explain the high CO2 selectivity in CO2/CH4 mixture and high C2H2 selectivity in C2H2/CH4 mixture. Energy decomposition analysis reveals that electrostatic energy, exchange energy, and repulsive energy are key factors in the binding strength of gas molecules on M-MOF-74. The preferential adsorption sites are confirmed to be located near the five-coordinate metal ions decorating the edges of the hexagonal channels. The elucidation of the adsorption mechanism at the molecular level provides key information for designing novel MOFs with high capacity and selectivity for CO2 from light hydrocarbon mixtures.